1. Field of the Invention
The invention relates to large acoustic array structures.
2. Description of the Related Art
The use of acoustic arrays deployed below the water's surface has a variety of applications in both military and commercial fields. A commercial application consists of using such an array to receive reflected acoustic signals in oil exploration surveys. Submarine detection is the principle use in the military field. The size of these acoustic devices varies depending on the application. The greater the desired performance, the more electro-acoustic transducers required. When multiple electro-acoustic transducers are used, also known in the industry as hydrophones, they are usually positioned in either a vertical or horizontal line array. After deployment, a line array has the ability to listen in certain selected narrow beams which improves the signal to noise ratio so that longer detection ranges are achieved with improved discrimination.
Deployment of a typical line array is provided in U.S. Pat. No. 3,944,964, issued to Loeser et al. on Mar. 16, 1976. Loeser et al. discloses a self-deploying and self-aligning linear acoustic detector for providing advanced listening capability based on the ability of the detector to listen in selected acoustic beams.
U.S. Pat. No. 5,056,065, issued to Bruengger on Oct. 8, 1991, discloses another method for deploying a horizontal line array. This disclosure teaches a system for rapidly deploying a line array from a sonobouy and positioning of the array horizontally at a desired depth below the water's surface and in accordance with a predetermined time period.
Deployment of re-useable vertical or horizontal line arrays typical in the industry are easily handled and deployed on a ship because of their manageable size and weight. A re-useable array provides a greater utility since it can be used more than one time and at more than one location. For those devices that are not reusable, replacement costs become a consideration factor. An example of a non-reusable line array is the Loeser et al. acoustic detector, which is designed to be air dropped for quick reaction to a military threat. In this situation, rapid deployment over large distances is required without the need for a waterborne platform. But for those linear arrays that are reuseable, retraction from the water and easy storage on ships permits a feasible and cost effective approach in the acoustical detection of underwater signals.
While the use of re-usable linear and vertical arrays is desirable, it has been found that the management of these systems is limited to a particular size. Once the size of an array become too great, it becomes impractical to deploy and retrieve the array on board a ship. Of course, the size of the array also determines the number of hydrophones that can be effectively utilized using prior art designs. An array design having more than 150 hydrophones which can be stored in a compact fashion on a ship, then deployed and later retrieved for many cycles is not found in the prior art.